#jewellery

Gemstone weight maths as an API, computed locally and deterministically — the carat, gram, point and measured-weight numbers a jeweller, gem dealer, appraiser or lapidary works to. The carat-to-grams endpoint converts a carat weight to grams, milligrams and points: the metric carat is exactly 0.2 g (200 mg) and is split into 100 points, so a 1.5 ct stone is 0.3 g and 150 points and a quarter-carat is a twenty-five pointer — the carat is a mass unit, not a size, so a 1 ct diamond and a 1 ct emerald weigh the same but look different because their densities differ. The grams-to-carat endpoint inverts it (divide grams by 0.2, or multiply by 5), for a weight taken on a gram balance. The round-brilliant-weight endpoint gives the trade estimate used when a stone is set and cannot be put on a scale: carat ≈ diameter² × depth × 0.0061, with the girdle diameter and total depth in millimetres — a 6.5 mm round about 4 mm deep estimates near 1 carat, which is exactly why a 1 ct round brilliant measures roughly 6.5 mm across; the factor can be nudged for a thick girdle or a different cut. Everything is computed locally and deterministically, so it is instant and private. Ideal for jewellery and appraisal tools, gem-dealer and auction apps, and lapidary calculators. Pure local computation — no key, no third-party service, instant. Weight maths only — it does not price the stone or grade the colour and clarity. 3 compute endpoints. For gold karat and fineness use a gold-purity API.

api.oanor.com/gemstone-api

Gold purity and karat maths as an API, computed locally and deterministically — the karat, fineness and alloy numbers a jeweller, goldsmith, assayer or refiner works to. The karat-to-fineness endpoint converts between the two purity systems: karat is the number of 24ths of a piece that is pure gold, so the fineness (parts per thousand, the figure on a hallmark stamp) = karat ÷ 24 × 1000 and the gold percentage = karat ÷ 24 × 100 — 24K is pure (1000‰), 18K is 750‰ (75 %), 14K is 583‰, 9K is 375‰. The pure-gold-weight endpoint gives the actual fine gold in a piece = its total weight × the gold fraction (karat ÷ 24): a 10 g 18K ring holds 7.5 g of gold and 2.5 g of alloy, the fine-gold content a refiner pays on and the basis of the intrinsic metal value. The alloy-mix endpoint inverts it for the bench: to bring refined fine gold down to a target karat, the total weight = the fine gold ÷ (target karat ÷ 24) and the alloy to add = the total − the fine gold, so 7.5 g of pure gold makes 10 g of 18K with 2.5 g of master alloy. Everything is computed locally and deterministically, so it is instant and private. Ideal for jewellery and goldsmithing tools, pawn and scrap-gold apps, and assay and metal-value calculators. Pure local computation — no key, no third-party service, instant. Purity maths only — it does not fetch the live gold price. 3 compute endpoints. For a metal part's weight from its dimensions use a metal-weight API.

api.oanor.com/goldpurity-api